Nancy Astor, the first female MP, by John Singer Sargent/Wikimedia

The next Parliament looks set to have the highest number of female MPs since women were first allowed to stand for election in 1918.

In a new report, the Electoral Reform Society has projected that 29.5% of MPs will be women following May’s general election. It’s an important advance, but it still falls far short of the parity necessary if the House Commons is to be truly representative of the electorate. After all, it is over 95 years after the Parliament (Qualification of Women) Act was passed, which first allowed women to become MPs. The pace of change has been far too slow.

The increase at this general election is encouraging though, particularly compared to the snail-like pace of change in female representation throughout the 20th century. Until the 1990s, the percentage of female representatives languished in the single digits. The need to increase women’s representation is slowly being recognised by the political parties. But change isn’t quick enough – we can’t wait decades for equality. And in an age of increasing disenchantment with the status quo, people are questioning the ability of parliament to represent them.

There are also concerns about consolidating the gains that are being made. After the much-lauded increase of female representation in 1997, the number of women MPs actually fell in the following election. This illustrates the danger of thinking that a more equitable gender balance in one election means it will be maintained in the next; the quest for gender equality must continue to be pursued until full parity has been achieved.

One thing that is still holding women back in Westminster is our electoral system. Of incumbent MPs elected in 2001 or before who are standing again in 2015, under 15% are women; this figure drops to 11% of those who were elected in 1987 or before. These male ‘seat blockers’ – bolstered by our majoritarian First Past the Post electoral system – will remain effectively unchallenged unless we get a fairer voting system. Parties also need to open up their selection processes for the mostly-male MPs who have held their seat for decades.

Nonetheless, the arrival of 44 more female MPs in Westminster in May would be an important step in the pursuit of equality, and it is the result of unflagging efforts to realise the goal of a truly representative parliament.

But there is little room for complacency: the presence of female representatives needs to be copper-fastened into the make-up of our representative institutions – and our voting system. After all, even with the predicted increase in female parliamentarians in May, more than 70% of the MPs will still be men. We can’t allow this to become the new ‘glass ceiling’ for women in Parliament. Let’s reform the system so that the progress we see this May will continue in 2020 and the years to come.

Read about the ERS’s new report, Women in Westminster